Congratulations!
Essentials:
xpen, piddle pads (maybe baby gates and crate too depending on your home/training)
food and water bowls
comfy bed
comb and brush (see Mimimomo's site
toplinepet.com)
baby toothbrush
small clippers (I use a mustache trimmer to tip ears)
notebook binder to keep essential documents like vet records
harness -- this one is tough because you need to know your pup's exact measurements. If really small, you can start with a kitty or ferret harness.